From 86f058287faae50caeb6d785aaca0dbb1f1e62b2 Mon Sep 17 00:00:00 2001
From: Slobodan Predolac <spredolac@fb.com>
Date: Thu, 30 Apr 2026 15:42:19 -0700
Subject: [PATCH] Restore errno save/restore in
 pages_purge_process_madvise_impl

TODO comment focused on free only, but this path is reachable via
other calls and it is safer to leave errno preservation here.
---
 src/pages.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/pages.c b/src/pages.c
index bec1cfdc..4bca965a 100644
--- a/src/pages.c
+++ b/src/pages.c
@@ -662,6 +662,7 @@ pages_purge_process_madvise_impl(
 		return true;
 	}
 
+	int    saved_errno = get_errno();
 	size_t purged_bytes = (size_t)syscall(JE_SYS_PROCESS_MADVISE_NR,
 	    PIDFD_SELF, (struct iovec *)vec, vec_len, MADV_DONTNEED, 0);
 	if (purged_bytes == (size_t)-1) {
@@ -671,6 +672,7 @@ pages_purge_process_madvise_impl(
 			atomic_store_b(
 			    &process_madvise_gate, false, ATOMIC_RELAXED);
 		}
+		set_errno(saved_errno);
 	}
 
 	return purged_bytes != total_bytes;